using System;

using System.Collections.Generic;

using System.Threading.Tasks;

​

public class Program

{

    public static void Main()

    {

        var accounts = GenerateAccount();

        var accountsProcess = new List<Account>();

        var taskList = new List<Task>();

        var batch = 4;

        var count = 0;

        foreach (var account in accounts)

        {

            if (count == batch)

            {

                var bob = accountsProcess;

                taskList.Add(new Task(() => ProcessAccount(bob)));

                count = 0;

                accountsProcess = new List<Account>();

            }

​

            count++;

            accountsProcess.Add(account);

        }

​

        Parallel.ForEach(taskList, t =>

        {

            t.Start();

        }

​

        );

        Task.WaitAll(taskList.ToArray());

        if (accountsProcess.Count > 0)

            ProcessAccount(accountsProcess);

    }

​

    public static List<Account> GenerateAccount()

    {

        var accounts = new List<Account>();

        var first = "First";

        var second = "Second";

        for (int i = 0; i <= 1000; i++)

        {

            var account = new Account();

            account.first = first + i;

            account.second = second + i;

            accounts.Add(account);

        }

​

        return accounts;

    }

​

    public static void ProcessAccount(List<Account> accounts)

    {

        Console.WriteLine(accounts.Count);

        foreach (var account in accounts)

        {

            Console.WriteLine(account.first + account.second);

        }

    }

}

​

public class Account

{

    public string first;

    public string second;

}